Ships can be measured in terms of overall length, length of the waterline, beam (breadth), depth (distance between the crown of the weather deck and the top of the keelson), draft (distance between the highest waterline and the bottom of the ship) and tonnage.

As well as being the generic word, "ship" also has a specific meaning: a vessel with bowsprit and three masts, each with topmast and topgallant mast and all square rigged. (See Full-rigged ship.)